I don't think it will help at all to know the linked server that is referenced.
The OP should try a
SELECT TOP 1 AUFNR FROM afpo
SELECT TOP 1 AUFNR FROM afko
SELECT TOP 1 AUFNR FROM s022
to verify which one fails.
Then use SELECT * FROM the_table_in_question
Finally, take a Baseball bat and practice at the "Submit-And-Pray"-Dptmt....